Bar codes are expressed as a pattern of bars and spaces of varying widths that represent digits, letters, or other symbols. In retail stores and warehouses, items are often identified through the use of bar codes, and store and warehouse personnel often use and are familiar with bar code readers that read bar codes. The particular way in which bars and spaces are arranged is called a symbology, of which there are many. The Universal Product Code (UPC) and its counterpart, the International Article Numbering Association Code (EAN), are extensively used in retail applications. Very popular in industrial, medical and government applications is Code 39, an alphanumeric symbology with self-checking properties that offers a variable length and a high degree of data security. Bar codes may be printed directly on items to be scanned or on labels that are attached to the item.
Typically, a bar code reader is used to illuminate a bar code symbol using an infrared or visible light source. Dark bars absorb the light, and the white spaces between the bars reflect the light back into the reader. A light detector in the reader transforms the presence or absence of light reflections into electrical impulses which represent the bar and space pattern in the bar code. A decoder translates the electrical impulses into a binary code which is transmitted to a PC or other controller or host computer system. The decoder may be integrated with or separate from the reader. Readers typically use visible and infrared light-emitting diodes (LED), helium-neon lasers, or solid-state laser diodes (visible and infrared) to illuminate the bar code symbol. Some readers employ charge-couple devices (CCD) which electronically "sees" the whole symbol at once. Two-dimensional CCD readers are used to read matrix symbologies. Some readers require close contact with the bar code being read, while others may read the bar code from distances up to several feet. Some readers are stationary, while others are hand-held. A bar code scanner is typically a bar code reader that uses a narrow laser beam that "scans" over a bar code, usually by reflecting the laser beam off of a small mirror within the reading device.
Electronic labels, such as Electronic Shelf Labels (ESL), are often used together with bar code identification to identify and provide information about items. These label typically have a receiver to receive initialization information and price update information, as well as a transmitter to send back information such as acknowledgment information and additional data, such as is described in applicant/assignee's U.S. patent application Ser. Nos. 08/839,839, 08/632,576, 08/699,375, and PCT applications PCT-IL-97/00339, and PCT-IL-97/00192. The receiver and transmitter are typically wireless, employing RF or optical communications means. In retail stores, electronic labels are often used and are initialized and updated by store personnel. For that purpose, store personnel typically carry portable terminals that communicate with the electronic labels.
A primary disadvantage of known bar code systems and electronic label systems when collectively considered is that separate communications devices are currently employed for bar code scanning and electronic label communications. In addition, bar code scanning with hand-held devices usually requires relatively accurate aiming in terms of both position and angle with respect to the bar code being read. This presents a major limitation with regard to self-scanning systems where store shoppers, not skilled in bar code reading, are provided with a hand held devices that include bar code readers. The shoppers often become frustrated by the difficulties in aiming the bar code readers and in scanning wrinkled, worn, or wet bar code labels. In addition, while it is known to display bar codes on Liquid Crystal Displays, the use of such displays is disadvantageous in that the display must be of a very high resolution and contrast, and must have a large number of display lines to effectively display a bar code, all rendering such displays too expensive for mass implementation in electronic labels.
The following U.S. patents are believed to represent the state of the art of bar code systems and electronic label systems: U.S. Pat. Nos. 4,002,886, 4,139,149, 4,387,297; 4,409,470, 4,521,677, 4,760,248, 4,766,295, 4,782,219, 5,019,811, 5,313,569, 5,345,071, 5,361,871, 5,382,779, 5,457,307, and 5,572,653.